\section{Interactions}
\begin{figure}
	\centering
		\includegraphics[width=\linewidth]{fig/move.png}
	\caption{Drag a disk around and release it: the disk join the group in a different spot.}
	\label{fig:move}
\end{figure}

ReportViz aims to provide engaging experiences for topic exploration. Currently, it allows a viewer to:
\begin{description} 
\item \textbf{Drag and release}: The viewer can interfere with the layout by dragging a disk around and releasing it. Then the disk joins the group in a different spot driven by the physics-inspired algorithm, as shown in Fig.~\ref{fig:move}.  
\item \textbf{Expand and collapse}: The viewer can select a tree node to expand or collapse it. Expanding a topic node spawns a group of key term nodes, as shown in Fig.~\ref{fig:overview}.     
\end{description}

Also the user can switch to the animation mode to play a synthesized topic fluctuation where disks are changing their radius periodically while they remain repelled and gathered.~(Bias can be adjusted in a default range for faster or slower convergence of the layout).   

\section{Feedbacks}

Preliminary experiments with ReportViz suggest it as a utility providing an overview of topics and key words in public health. We summarize feedbacks from users of ReportViz as follows: 

\begin{description}
\item \textbf{Topic complexity}: multiple topics could be nested in a broader theme. For example, in Health 2011~\cite{Health:2012}, ``Expenditure'' and ``Programs'' are bundled as ``Health Care Cost'', while they remain separated topics in Health 2008~\cite{Health:2009}, 2009~\cite{Health:2010} and 2010~\cite{Health:2011}; In particular, the topic ``Expenditure'' is splitted into ``National Expenditure'' and ``State Expenditure'' in Health 2008~\cite{Health:2009}. 

\item \textbf{Word choices}: words represent the same concept are used across different topics. For example, ``cancer'' is a key word in the topic ``Measure of Health'' while ``maglignant neoplasm'' is used in the topic ``Mortality''. 
    
\end{description}
  
\section{Conclusion}
In this paper we present ReportViz, a utility that integrates text mining and topic visualization. We propose to use the tree data structure for topic merge and split, physics-inspired algorithms for the layout, and animation for incorperating time-varying features.   
In the future, we would like to build ReportViz as a full-fledged navigation tool for health documents. Specifically, we would like to encode more attributes, such as word-to-topic specificity and topic-to-topic correlation into the visualization. It would also be interesting to design use cases to evaluate the effectiveness of ReportVis for understanding topic complexity and word choices in public health. 




\begin{table*} 

\renewcommand{\arraystretch}{2}\addtolength{\tabcolsep}{-1pt}
\begin{center}
\begin{tabular}{|l|p{8.6cm}|}
\hline
\textsc{\Large Topics} & \textsc{\Large Lists of Key terms} \\ \hline
Population & level, \textbf{age}, \textbf{sex}, \textbf{race}, \textbf{resident}, poverty, Hispanic, \textbf{\color{red}income}, \textbf{origin} \\ \hline  
Fertility and Natality & \textbf{weight}, \textbf{\color{red}height}, childbearing, prenatal, birth, breastfeeding, \textbf{pregnancy}, \textbf{abortion}, \textbf{contracept}, marital
\\ 
\hline
Mortality & \textbf{cause}, \textbf{injuries}, homicide, suicide, \textbf{cardiovascular}, \textbf{malignant neoplasm}, trachea, bronchus, breast, HIV, drug, expectancy, fetal, \textbf{diseases}, \textbf{\color{red}accidental death}\\
\hline
Measure of Health &
\textbf{occupation}, illness, industry, condition, geography, survival, heart, stroke, diabetes, headache, pain, joint, activity, cancer, limitation, vision, hearing, assess, disability, \textbf{urbanization}, distress, \textbf{smoking}, education, \textbf{drinking}, hypertension, cholesterol, \textbf{nutrient}, leisure, obesity, dental \\
\hline
Ambulatory Care &
\textbf{prescription}, urbanization, access, visit, clinic, influenza, \textbf{vaccination}, coverage, pneumococcal, dental, mammography, pap smears, procedures, \textbf{emergency}, \textbf{\color{red}X-ray}, physician, hospital, outpatient, primary, dietary, supplement, \textbf{\color{red}blood tests}, \textbf{\color{red}rehabilitation}
\\
\hline
Inpatient Care &
hospital, \textbf{admissions}, discharges, nonfederal, short-stay, \textbf{diagnosis}, \textbf{length of stay}, procedure, \textbf{surgery}, \textbf{specialty} \\
\hline
Personnel &
\textbf{physician}, \textbf{patient}, \textbf{doctors}, medicine, primary, \textbf{specialty}, dentists, \textbf{employment}, wages, enrollment, graduates, schools \\
\hline
Facilities &
\textbf{hospitals}, \textbf{beds}, occupancy, ownership, organization, treatment, community, nursing, homes, medicare, certified, providers, suppliers, \textbf{MRI (Magnetic resonance imaging)}, \textbf{CT (computed tomography)}\\
\hline
Expenditures &
\textbf{GDP (gross domestic product)}, national, \textbf{CPI (Consumer Price Index)}, growth, services, annual, \textbf{expenses}, payment, out-of-pocket, \textbf{insurance} \\
\hline
Coverage and Programs &
Insurance, private, \textbf{medicaid}, \textbf{medicare}, enrollees, FFS (fee-for-service), \textbf{beneficiaries},  eligibility, veterans, state, poverty, fiscal, \textbf{\color{red}reimbursement}\\
\hline
\end{tabular}
\end{center}

\caption{We show in the left column a list of topics addressed in health reports. On the right column we show lists of key words associated with each topics. The terms shown in black are summarized from text. The words highlighted in bold are selected by medical students as terms with higher specifity. Words shown in red are considered related, but not reported from text analysis.}
\label{tab:health_topics}
\end{table*}
